Form copying method and apparatus

ABSTRACT

Method and apparatus for reproducing in a workpiece the form of a template by moving a rod over the workpiece in unison with the movement of a topped stylus over the template and in which the stylus tip is cast in situ in a mould formed by the tool itself.

O United States Patent [151 3,683,560 Hallewell [4 1 Aug. 15, 1972 [54]FORM COPYING METHOD AND [56] References Cited APPARATUS UNITED STATESPATENTS [72] Inventor: Bernard Fredrlck l-lallewell, llillmgdon, England2,477,135 7/1949 Marker ..5l/ 100 2,956,377 10 1960 White ..51 100 [73]Assgnee Twlmasm" 3 035 565 51962 Noble 51/160 x England [22] Filed: July13, 1970 Primary Examiner-Harold D. Whitehead [21] AppL Nu: 54,221Attorney-Woodhams, Blanchard and Flynn F i A H ti Pr [57] ABSTRACT [30]ore gn pp m on f Dam Method and apparatus for reproducing in a workpieceJuly I969 Great Bl'ltalfl the form of a template by moving a rod overthe workpiece in unison with the movement of a topped stylus U-S. Clo R5 over the template and in which the tylus i cast in [51] Int. Cl...B24b 17/02 sit in a mould f d by the tool it lfi [58] Field of Search..51/5, 100, 281

12 Clains, 2 Drawing Figures Patented Aug. 15, 1972 2 Sheets-Sheet 1Patented Aug. 15, 1972 2 Sheets-Sheet 2 FORM COPYING METHOD ANDAPPARATUS This invention relates to a 1/ 1 form copying device.

In a conventional l/l copying arrangement the tool is mounted over thejob and a similar size and shape stylus or follower is mounted over atemplate or master. The tool and stylus are constrained to move togetherso that if the stylus is made to exactly follow the template then thetool will produce the same shape in the job within the'accuracy allowedby the similarity between tool and stylus. During the cutting operation(particularly on a grinding machine) the tool may wear so that thefinished accuracy will .be limitedby variation in tool and stylus sizes.

According to one aspect of the invention correction for tool wear isaccomplished'by casting or recasting the stylus tip as required in amould produced by the tool itself. The stylus will then be an exactreplica of the tool and if all operations take place upon the machinethen the tool and stylus will automatically be in alignment.

In the case of a grinding machine the template, master or piece part tobecopied may be affixed to a specially made location area on anattachment mounted on the grinding machine table or ways. Thisattachment consists of the stationary location table for the templateand a work table which'is aligned with the template table and able toreciprocate longitudinally on slides so as to always remain aligned withthe template table. In operation this work table is caused toreciprocate .by hand or any suitable power source (e.g. electric,hydraulic or pneumatic) under the grinding wheel so allowing the workpiece to be ground.

When a stylus is to be cast to match the grinding wheel a piece ofeasily machined material is mounted on the template platform and bymovement of the longitudinal slide of the machine is brought under thegrinding wheel.

This piece of material then has a slot ground in it exactly matching thegrinding wheel profile. By moving only the longitudinal slide of themachine this ground mould is arranged under the stylus so that in thetransverse and vertical directions the slot remains aligned with thewheel. A stylus tip is then cast in situ in this slot so as to beattached to the bottom of the stylus arrangement. The casting medium maybe any suitable durable and non-distorting hardenable material. Anindicator is connected to the stylus to measure its vertical deflection.The reading of this indicator is taken while the stylus tip is still inthe mould, and this reading is used as zero in subsequent grindingoperations. Grinding operations may then be continued by following thetemplate with the stylus and maintaining the indicator reading at zeroby adjusting transverse and vertical machine slides. This procedure ofgrinding a mould with the wheel and casting a new stylus tip in situ may'be repeatedas and when required so as to compensate for wheel wear.

In a preferred embodiment provision is made for mounting a profileddressing block on the template platform or machine wheelhead, the wheelthen being readily and quickly re-formed to its required shape bypassing it through this block. This is particularly useful where toolwear is considerable, e.g. when using a conventional aluminum oxide orsilicon carbide wheel.

Instead of a profiled block, a radius/tangent dresser may be similarlymounted on the template platform or machine wheelhead.

Where the wheel is one which can be readily dressed, and a dresser suchas a profiled dressing block or a radius/tangent dresser is provided, itmay be preferable to compensate for wheel wear by redressing the wheeland then re-zeroing the initially cast stylus tip in the initiallyformed mould, rather than by grinding out a new mould with the .wornwheel and casting a new stylus tip in this fresh mould; in thisprocedure the redressed wheel of course corresponds exactly in profileto the original wheel and hence to the initially cast stylus tip, andremains in alignment with the latter, so that recasting of the tip in amould ground by the redressed wheel is generally not necessary,re-zeroing of the tip being adequate.

The stylus is preferably supported by spaced flexible spring steelstrips. This arrangement is ideal for this purpose having no friction orsusceptibility to wear, but allowing the required degree of verticalmovement together with maximum transverse stability.

The attachment carrying the work table and template table is preferablymounted on trunnions so that the work table and template table assemblymay be swung about a longitudinal center line. This allows for morefavorable grinding approach to some work pieces, allowing the face ofthe grinding wheel to be used rather than the sides. This produces abetter grinding condition and also limits inaccuracies in copying due toside deflections of the wheel or stylus. This pivotal mounting of thework table and template assembly is of similar advantage withconventional form copiers in which no provision is made for recastingthe stylus tip in situ in a mould ground by the wheel.

The copying arrangement described is also suitable for automatic copyingusing any of the established means by coupling the stylus to the controlsystem sensor and allowing the control system to activate the machinevertical feed.

In another application of the invention, the reciprocating work tabledescribed above is replaced by a rotary workhead mounted to permitcylindrical work to be copymachin'ed.

The invention, particularly applicable to grinding machines, but alsoapplicable to a variety of other machine tools thus provides a formcopying method and apparatus in which a tool moves in unison with themovement of a stylus over a template to reproduce the template form on aworkpiece and in which the stylus tip is cast or recast as necessary insitu in a mould formed by the tool itself. The invention also provides acarriage for attachmentto such apparatus and carrying the work table andtemplate platform, and means for mounting the mould blank on thetemplate platform. There is also provided form copying apparatus inwhich a tool "moves in unison with the movement of a stylus over atemplate to reproduce the template form on a workpiece, the workpiecetable and template platform being mounted so that they can be swungabout a longitudinal center axis to permit optimum approach of the toolto the workpiece.

An embodiment of the invention is illustrated in the accompanyingdrawings in which FIG. 1 is a side elevation, partly in section, showingdiagrammatically parts of a grinding machine, and

FIG. 2 is an end elevation, in section, along lines 2- 2 of FIG. 1.

In the drawings a portion of a conventional surface grinding machine isindicated generally at 2, the machine table 3 having a support 5 fixedlymounted thereon, which in turn has pivotally mounted thereon a carriage4 carrying a worktable 6 and a template platform 8. The worktable 6 isslidably supported on the guide rods 7. A rotatable grinding wheel 10 issupported over the carriage 4 on a support member 11 for grinding aworkpiece 12. The table 3, asis conventional with surface grinders, ismovably mounted on the machine frame by means of a cross-slide forpermitting the table to move longitudinally and transversely under thegrinding wheel, and the grinding wheel is likewise mounted so as to bemovable toward and away from the table to permit the grinding wheel tobe moved into engagement with the workpiece mounted on the table. Thesemovements of the grinding wheel and of the worktable are conventionalwith surface grinders, as disclosed in U. S. Pat. No. 3,324,493 Thetemplate platform carries a template 14 whose form is to be copied, anda stylus 16 which is moved over the template surface. The stylus ismounted on two spaced flexible steel spring strips 18 which permitvertical movement of the stylus as it rides over the template thesprings 18 in turn being mounted on the support member 11. The grindingoperation is conducted in the conventional manner; the verticaldeflection of the stylus is shown on an indicator dial 20, and thereading on this dial is maintained constant while the wheel and stylusare constrained to relatively move together over the workpiece andtemplate respectively so that the wheel produces on the workpiece aprofile corresponding to that of the template. Normally tool wear limitsthe accuracy of profile reproduction, but this is overcome according tothe invention by employing a stylus tip 22 which is cast in situ tocorrespond exactly to the profile of the wheel. A block 24 of easilyground material, eg easily ground metal, is mounted on the templateplatform in alignment with the grinding wheel and by movement of thelongitudinal slide (not shown) of the a machine is brought under thewheel 10, which then cuts in the block 24 a slot corresponding exactlyto its own profile. By movement of the longitudinal slide the resultingmould is then brought under the stylus and the tip 22 is then cast inthe mould and on the end of the stylus, using any suitable castingmaterial, e.g. a hard wax. The stylus tip thus cast is an exact replicaof the wheel. The reading on the indicator dial is taken as the zero forsubsequent grinding, this reading being maintained constant as thetemplate is brought under and into contact with the stylus tip andduring the grinding of the workpiece. The stylus tip is removed and afresh one cast (using of course a freshly formed mould in each case) asoften as is necessary according to tool wear e.g. before or even duringa grinding operation. In the embodiment illustrated the templateplatform also carries a diamond profiled dressing block 26; when wheelwear has become excessive the wheel is readily re-formed to the requiredprofile by passing it through the dressing block, this operation beingfollowed by rezeroing the existing stylus tip in the existing mould orby casting a fresh stylus tip in a fresh mould as described above.

The carriage 4 is mounted on trunnions 28, permitting the workpiece andtemplate thereon to be swung in unison about the longitudinal trunnionaxis. This permits the most advantageous angle of attack of the wheel tothe workpiece to be maintained; i.e. the whole carriage, with workpieceand template, can be pivoted relative to the wheel and stylus so thatinclined surfaces of the profile can be ground with the periphery ratherthan with the sides of the wheel, the template adopting the sameorientation relative to the stylus. As indicated above, this feature ofpivotal mounting of the carriage is equally of advantage withconventional form-copying equipment.

In a further embodiment of the invention the reciprocating tabledescribed above is replaced by a rotary workhead, whose axis of rotationlies across the carriage 4, so allowing cylindrical work to be copymachined.

I claim:

1. In a form copying method in which a tool is constrained to move overa workpiece in unison with the movement of a tipped stylus over atemplate to reproduce the template form on the workpiece, theimprovement which comprises casting or recasting the stylus tip in amould formed by the tool itself.

2. In a method according to claim 1 the further improvement of effectingthe formation of the mould by the tool and the casting of the stylus tipon the same machine as the form copying operation so that tool andstylus are in alignment.

3. In a method according to claim 1 wherein the tool is a grinding wheelon a surface grinding machine, the template is mounted on the grindingmachine on a template table and the workpiece is mounted on the grindingmachine on a worktable, said worktable being reciprocable in alignmentwith the template table, the improvement of casting said stylus tip bymounting a block of machinable material on the template platform,bringing said block under the grinding wheel and grinding therein a slotmatching exactly the grinding wheel profile thereby forming a mould forthe stylus tip, bringing this mould under the stylus with the slot inprecise alignment with the grinding wheel, and casting in the slot astylus tip attached to the stylus, whereby the stylus tip is a replicaof the grinding wheel profile and is in precise alignment with thegrinding wheel.

4. In a method according to claim 3 wherein an indicator is connected tothe stylus and measures its vertical deflection, the improvement oftaking the reading of the indicator while the cast stylus tip is stillin the mould and maintaining this reading of the indicator as the stylustip follows the template in subsequent grinding operations.

5. In a method according to claim 3 the further improvement of grindinga fresh mould and casting a new stylus tip in said new mould when saidwheel becomes worn, thereby to compensate for wheel wear.

6. In a method according to claim 4 the improvement which comprisesmounting a dresser on the machine and compensating for wheel wear byre-forming the worn wheel to its original profile with the dresser,disposing the initially cast stylus in the initially formed mould andadjusting the vertical deflection until the indicator gives the saidreading.

7. In a method according to claim 3 the improvement of mounting theworktable and template table on an attachment mounted on trunnionswhereby said tables can be swung in unison about a longitudinal centerline, and swinging the tables about this line during the form copyingoperation to maintain an optimum orientation of the workpiece to thegrinding wheel.

8. In a surface grinding machine having a rotatable grinding wheelmounted over and relatively movable toward and away ,from a machinetable provided with transverse slides and with means for selectivity andcontrolledly moving the machine table on said slides relative to saidwheel, the improvement which comprises:

a template platform mounted fixedly relative to the machine table;

a worktable mounted below the grinding wheel for reciprocationlongitudinally of the machine relative to the grinding wheel, templatetable and machine table;

'a stylus mounted resiliently above the template table for verticalmovement relative to the grinding wheel, template table and machinetable;

means for mounting on said template table a moulding block in registerwith said grinding wheel; and

means for registering vertical deflection of the stylus relative to thegrinding wheel; whereby said moulding block can have a slot formedtherein by said grinding wheel, with a tip for said stylus then beingformed in said moulding block so that said stylus is identical to saidgrinding wheel. 9. A machine according to claim 8 wherein the stylus issupported by spaced flexible spring strips.

10. A machine according to claim 8 including an indicator connected tothe stylus for measuring the vertical deflection of the stylus.

11. A machine according to claim 8, wherein said worktable for theworkpiece and the template platform are mounted on trunnions for pivotalmovement together about an axis extending longitudinally of the machinetable.

12. An attachment for a form copying machine which comprises a basemember attachable to the machine table of the copying machine, atemplate table mounted on the member and a worktable mounted on themember for reciprocation relative to the template table, the worktableand template table each being mounted for pivotal movement in unisonabout an axis parallel to the direction of reciprocation of theworktable.

1. In a form copying method in which a tool is constrained to move overa workpiece in unison with the movement of a tipped stylus over atemplate to reproduce the template form on the workpiece, theimprovement which comprises casting or recasting the stylus tip in amould formed by the tool itself.
 2. In a method according to claim 1 thefurther improvement of effecting the formation of the mould by the tooland the casting of the stylus tip on the same machine as the formcopying operation so that tool and stylus are in alignment.
 3. In amethod according to claim 1 wherein the tool is a grinding wheel on asurface grinding machine, the template is mounted on the grindingmachine on a template table and the workpiece is mounted on the grindingmachine on a worktable, said worktable being reciprocable in alignmentwith the template table, the improvement of casting said stylus tip bymounting a block of machinable material on the template platform,bringing said block under the grinding wheel and grinding therein a slotmatching exactly the grinding wheel profile thereby forming a mould forthe stylus tip, bringing this mould under the stylus with the slot inprecise alignment with the grinding wheel, and casting in the slot astylus tip attached to the stylus, whereby the stylus tip is a replicaof the grinding wheel profile and is in precise alignment with thegrinding wheel.
 4. In a method according to claim 3 wherein an indicatoris connected to the stylus and measures its vertical deflection, theimprovement of taking the reading of the indicator while the cast stylustip is still in the mould and maintaining this reading of the indicatoras the stylus tip follows the template in subsequent grindingoperations.
 5. In a method according to claim 3 the further improvementof grinding a fresh mould and casting a new stylus tip in said new mouldwhen said wheel becomes worn, thereby to compensate for wheel wear. 6.In a method according to claim 4 the improvement which comprisesmounting a dresser on the machine and compensating for wheel wear byre-forming the worn wheel to its original profile with the dresser,disposing the initially cast stylus in the initially formed mould andadjusting the vertical deflection until the indicator gives the saidreading.
 7. In a method according to claim 3 the improvement of mountingthe worktable and template table on an attachment mounted on trunnionswhereby said tables can be swung in unison about a longitudinal centerline, and swinging the tables about this line during the form copyingoperation to maintain an optimum orientation of the workpiece to thegrinding wheel.
 8. In a surface grinding machine having a rotatablegrinding wheel mounted over and relatively movable toward and away froma machine table provided with transverse slides and with means forselectivity and controlledly moving the machine table on said slidesrelative to said wheel, the improvement which comprises: a templateplatform mounted fixedly relative to the machine table; a worktablemounted below the grinding wheel for reciprocation longitudinally of themachine relative to the grinding wheel, template table and machinetable; a stylus mounted resiliently above the template table forvertical movement relative to the grinding wheel, template table andmachine table; means for mounting on said template table a mouldingblock in register with said grinding wheel; and means for registeringvertical deflection of the stylus relative to the grinding wheel;whereby said moulding block can have a slot formed therein by saidgrinding wheel, with a tip for said stylus then being formed in saidmoulding block so that said stylus is identical to said grinding wheel.9. A machine according to claim 8 wherein the stylus is supported byspaced flexible spring strips.
 10. A machine according to claim 8including an indicator connected to the stylus for measuring thevertical deflection of the stylus.
 11. A machine according to claim 8,wherein said worktable for the workpiece and the template platform aremounted on trunnions for pivotal movement together about an axisextending longitudinally of the machine table.
 12. An attachment for aform copying machine which comprises a base member attAchable to themachine table of the copying machine, a template table mounted on themember and a worktable mounted on the member for reciprocation relativeto the template table, the worktable and template table each beingmounted for pivotal movement in unison about an axis parallel to thedirection of reciprocation of the worktable.